Hydraulic fluids are fluids which are used to offer resistance in hydraulically operated mechanisms. The main classes of hydraulic fluids commonly used are petroleum-based [See U.S. Pat. No. 4,566,994 and U.S. Pat. No. 4,800,030] (composed of chemically saturated or unsaturated, straight-chained, branched or ring-type hydrocarbons [See U.S. Pat. No. 5,236,610]), water/glycol solutions, and water-in-oil emulsions [See U.S. Pat. No. 3,236,778].
There are several notable disadvantages to these conventional types of hydraulic fluids. The petroleum-based hydraulic fluids pose certain environmental and health risks. In addition, petroleum oils may be the least fire-resistant and attempts to improve fire-resistance by the addition of fire-resistant compounds tends to reduce lubricity. Petroleum is a non-renewable and limited natural resource. Moreover, petroleum oil allowed to escape into the ground causes soil and groundwater contamination which can pose additional health and environmental problems.
Water-based hydraulic fluids have disadvantages as well. Hydraulic fluids of this type often lack sufficient mechanical stability and lubricity to operate at high temperatures and pressures.
There is a need for hydraulic fluids which are based on renewable natural resources and which simultaneously have the characteristics of desirable viscosity, lubricity, stability, and volatility while reducing potential harm to the environment.